Method and apparatus for removing vinyl monomers from a gas stream

ABSTRACT

An apparatus for removing vinyl monomers from a gas stream includes a tube, a shading casing and a light emitting unit. The tube includes a first section having a connecting port with an opening, a second section, and a third section having an outlet. The three sections sequentially link together, with the second section connecting between the first section and the third section. A photoactive-inorganic medium is arranged inside the second section. The shading casing surrounds and seals the second section and an inner surface of the shading casing defines a reflecting face. The light emitting unit is mounted to the shading casing to irradiate and activate the photoactive-inorganic medium in the second section. Accordingly, the photoactive-inorganic medium can be activated by the light emitting unit to photocatalyze vinyl monomers in a gas stream to polymerize on surfaces of the photoactive-inorganic medium, such that vinyl monomers are removed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and an apparatus for thetreatment of exhaust gas and, more particularly, to a method and anapparatus for removing vinyl monomers from a gas stream.

2. Description of the Related Art

Generally, there are three chemical reactors in chemical engineering,which are continuous stirred-tank reactor (CSTR), plug flow reactor(PFR) and pack-bed reactor (PBR). According to aspects of chemicalengineering applications, these reactors are packed with catalysts andare often equipped with different units, such as a thermostat. Hence, adiversity of chemical reactors is designed. Key process variables forthe design of a chemical reactor include flow rate, temperature,concentrations of chemical species, pressure and so on. Furthermore, thefollowing are advantages and disadvantages of different kinds ofchemical reactors.

First, the CSTR is most used in industry and can be run steadily, withreagents inside a reaction tank of the CSTR being well mixed.Additionally, several CSTRs in series use will be operated for economicbenefit. However, in all kinds of continuous flowing reactors, CSTR hasa lowest volumetric unit of conversion and that leads to the necessityof a reaction tank with large volume to enhance volumetric unitconversion.

The PFR, which is constructed by a single tube or many tubes inparallel, is suitable for a gas fluid. It has a high volumetric unitconversion, which is the highest in all kinds of continuously flowingreactors, and can run for long periods of time without maintenance.Disadvantages of plug flow reactors are that temperatures are hard tocontrol due to exothermic reactions and can result in undesirabletemperature gradients.

The PBR has the highest volumetric unit of conversion in all kinds ofcatalytic reactors. However, it is also hard to control temperature ofthe PBR and to replace material of a catalyst packed in the PBR.

Moreover, in order to remove organic compounds from a waste gas stream,there is an adsorbent in an absorption tower that is an example of aconventional apparatus for treating exhaust, such as active carbon.Activated carbon is a selective adsorbent, which doesn't adsorb polarmaterial like water but does adsorb non-polar organic compounds withhigh molecular weights, because of its non-polarity. After adsorbingorganic compounds, activated carbon can be disposed in landfill with orwithout incineration process, or recovered. Recovered activated carbonis regenerated by heat, vacuum desorption or stripping desorption toreuse.

Nevertheless, said conventional apparatus for treating exhaust hasseveral drawbacks. The organic compounds are easily released from theactivated carbon when environmental factors, like light or temperature,change, because the organic compounds merely physically are adsorbed bythe activated carbon. Thus, saturated activated carbon should bedisposed in landfill or incinerated without recovery of the organiccompounds, so that using activated carbon costs much and the organiccompounds can not be reused. Besides, when the activated carbon issaturated, the adsorbing processes will be stopped for replacingabsorbent, such that the treatment is not continuous.

Taiwan Patent Issue No. 446572 entitled “APPARATUS AND METHOD FOR UVOXIDATION AND MICROBIOLOGICAL DECOMPOSITION OF ORGANIC WASTE AIR” isanother example of a conventional apparatus for treating exhaust anddiscloses a first UV oxidation reactor, a humidifying device, an acidneutralizing device and a bio-filter. The first UV oxidation reactorincludes an UV lamp for organic pollutants irradiation and a firstmonitoring device for detecting the concentration of the organicpollutants. The humidifying device and the acid neutralizer device has aspecific function to humidify the organic waste air and neutralize theacidity of the organic waste air respectively. The biofilter containsbiosolids with microorganisms capable of metabolizing or biodegradingone or more organic compounds and is used for treating residualpollutants after the first UV oxidation reactor. Therefore, an organicpollutant in organic waste air is photo-oxidized to reduce theconcentration of the organic pollutant.

However, these past developed apparatuses for treating exhaust gas arebased on the degradative oxidation reactions of organic pollutants byirradiating UV light. If some usable compounds, such as vinyl monomer,exist in the organic waste air, their degradation also occurs. Althoughan oxidant or a catalyst like ozone or titanium dioxide may be added inthe first UV oxidation reactor, degradation of organic pollutant isenhanced without recovery the usable compounds in the organic waste air.Furthermore, amount of free radicals for decomposition of organicpollutants and generated from the catalyst of TiO₂ is decreased to lowefficiency of degradation of the organic pollutants, while TiO₂ isexposed to light outside the first UV oxidation reactor. Hence, there isa need for an improvement over the conventional apparatus for treatingexhaust.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide a newpollution treatment for a gas stream, which solves the problems of theprior art described above to allow vinyl monomer recovery bypolymerization and reduction of consumption of energy by photocatalyticreaction.

To accomplish the above objective, the present invention provides amethod for removing vinyl monomers from a gas stream. The method forremoving vinyl monomers from a gas stream according to the preferredteachings of the present invention includes the steps of: irradiating aphotoactive-inorganic medium by a light emitting unit to activate thephotoactive-inorganic medium; and pumping a gas stream including vinylmonomers to contact with the activated photoactive-inorganic medium tomake the vinyl monomers in the gas stream to polymerize on thephotoactive-inorganic medium and jointly form a polymericnano-composite. Accordingly, recovery of vinyl monomers is achieved andvinyl monomers can be reused in the future.

The present invention further provides an apparatus for removing vinylmonomers from a gas stream. The apparatus according to the preferredteachings of the present invention includes a tube, a shading casing anda light emitting unit. The tube includes a first section that has aconnecting port with an opening, a second section, and a third sectionhaving an outlet. The three sections sequentially link together, withthe second section connecting between the first section and the thirdsection. A photoactive-inorganic medium is arranged inside the secondsection. The shading casing surrounds and seals the second section andan inner surface of the shading casing defines a reflecting face. Thelight emitting unit is mounted to the shading casing to irradiate andactivate the photoactive-inorganic medium in the second section.Accordingly, the photoactive-inorganic medium can be activated tophotocatalyze vinyl monomers in a gas stream to polymerize, such thatcost of treating gas pollution can be reduced.

Further scope of the applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferable embodiments of the invention, aregiven by illustrations only, since various will become apparent to thoseskilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be fully understood from the detaileddescription given herein below and the accompanying drawings which aregiven illustrations only, and thus are not limitative of the presentinvention, and wherein:

FIG. 1 is a side view illustrating an apparatus for removing vinylmonomers from a gas stream in accordance with a first embodiment of thepresent invention;

FIG. 2 is a partial, cross sectional view of the apparatus of FIG. 1according to section line 2-2 of FIG. 1;

FIG. 3 is a block diagram illustrating a method for removing vinylmonomers from a gas stream in accordance with a preferred embodiment ofthe present invention;

FIG. 4 is a diagram illustrating variations in styrene removalefficiency with time;

FIG. 5 is a diagram illustrating variations in molecular weights ofpolymers on a photoactive-inorganic medium of the apparatus of thepresent invention with temperature;

FIG. 6 is a side view illustrating an apparatus for removing vinylmonomers from a gas stream in accordance with a second embodiment of thepresent invention; and

FIG. 7 is a partial, cross sectional view of the apparatus of FIG. 6according to section line 7-7 of FIG. 6.

All figures are drawn for ease of explanation of the basic teachings ofthe present invention only; the extensions of the figures with respectto number, position, relationship, and dimensions of the parts to formthe preferred embodiment will be explained or will be within the skillof the art after the following teachings of the present invention havebeen read and understood. Further, the exact dimensions and dimensionalproportions that conform to specify the forces of weight, strength, andsimilar requirements will likewise be within the skill of the art afterthe following teachings of the present invention have been read andunderstood.

Where used in the various figures of the drawings, the same numeralsthat designate the same or similar parts. Furthermore, when the terms“first”, “second”, “inner”, “outer”, “lower”, “end”, “portion”, “axial”,“radial”, and similar terms are used herein, it should be understoodthat these terms have reference only to the structure shown in thedrawings as it would appear to a person viewing the drawings and areutilized only to facilitate describing the invention.

DETAILED DESCRIPTION OF THE INVENTION

An apparatus for removing vinyl monomers from a gas stream of a firstembodiment according to the preferred teachings of the present inventionis shown in FIGS. 1 and 2 of the drawings. According to the firstembodiment form shown, the apparatus for removing vinyl monomers from agas stream includes a tube 1, a shading casing 2 and a light emittingunit 3 for irradiating inside the shading casing 2, with the tube 1being partially received in the shading casing 2.

Referring again to FIGS. 1 and 2, the tube 1 of the first embodimentaccording to the preferred teachings of the present invention is made ofmaterials those does not react with gas, such as glass, quartz or metal.The tube 1 includes a first section 11, a second section 12 with one endthereof coupling to the first section 11, and a third section 13coupling to the other end of the second section 12; that is, the threesections 11, 12, 13 sequentially link together, with the second section12 connecting between the first and third sections 11, 13. The firstsection 11 has at least one connecting port 111 with an opening and atleast one first controlling valve 112. In this embodiment, an amount ofthe connecting port 111 is equal to that of the first controlling valve112, which are both four, as shown in FIG. 1, with each firstcontrolling valve 112 being mounted on each connecting port 111.Specifically, each of the connecting ports 111 is used for a gas streamto enter the first section 11 through the openings of the connectingports 111 while one of the connecting ports 111 is linked to a gassource (not illustrated), or for a gas inside the tube 1 to be exhaustedwhile one of the connecting ports 111 is linked to an exhauster like amotor (not illustrated). Besides, the controlling valves 112 are used tocontrol flow rate of the gas flowing into or out of the tube 1. There isa photoactive-inorganic medium 121 arranged inside the second section12, and preferably the photoactive-inorganic medium 121 is coated on aninner surface of the second section 12 or is in the form of a pluralityof particles packed in the second section 12. Hence, thephotoactive-inorganic medium 121 is selected from Nano-TiO₂, CarbonNanotubes (CNTs), Nano-Ag, Nano-Au, Nano-Cu, Nano-Pt or Nano-Fe. Seen inFIGS. 1 and 2, the photoactive-inorganic medium 121 is in the form of aplurality of Nano-TiO₂ particles packed in the second section 12. Thethird section 13 has an outlet 131 at a free end thereof withoutcontacting the second section 12, through which gas inside the tube 1flows out. A second controlling valve 132 is mounted close to the outlet131 to control flow rate of the gas flowing out of the tube 1 throughthe outlet 131.

The shading casing 2 of the first embodiment according to the preferredteachings of the present invention surrounds the second section 12 toshade the second section 12 from light of outer space, with the secondsection 12 being received and sealed in the shading casing 2, such thatlight outside the shading casing 2 entering the second section 12 toaffect function of the photoactive-inorganic medium 121 is avoided. Theshading casing 2 is preferred a hollow cylinder, and an inner radialsurface of the shading casing 2 and an outer radial surface of thesecond section 12 are spaced an interval apart. Furthermore, the shadingcasing 2 has two through holes 21 at two opposite ends thereof, whichthe tube 1 will pass through, an assembling hole 22 formed in a radialwall thereof, and a reflecting face 23 that is defined by the innersurface of the shading casing 2. In detail, the inner surface of theshading casing 2 is daubed with white paint or attached with white clothor paper to form the reflecting face 23.

The light emitting unit 3 of the first embodiment according to thepreferred teachings of the present invention is mounted on the shadingcasing 2 via the assembling hole 22, with the light emitting unit 3sealing the assembling hole 22. The light emitting unit 3 is able toemit UV or visible light. In the first embodiment, the light emittingunit 3 is able to emit UV light to activate the photoactive-inorganicmedium 121.

Now turning to FIGS. 1 through 3, a method for removing vinyl monomersfrom a gas stream by using the apparatus of the first embodimentincludes the following steps. First, a pretreatment of thephotoactive-inorganic medium 121 designated as step “S1” is proceeded,which is heating the photoactive-inorganic medium 121 at low pressure.Specifically, the photoactive-inorganic medium 121 of a predeterminedamount, for example a weight of 0.6 g, is received in the second section12 and the second section 12 is heated by a heater (not illustrated) torid the photoactive-inorganic medium 121 of water molecules and oxygenadsorbed thereon, such that function of the photoactive-inorganic medium121 is prevented from being influenced by moisture. And then theconnecting ports 111 are linked to a polluted gas source, an exhausterand an aerating gas source respectively (not illustrated), with one ofthe connecting ports 111 being closed and without linked. Only theexhauster is turned on to pump air out of the tube 1, so that the insideof the second section 12 can be in a pressure lower then 400 torr orclose to vacuum (lower than 0.1 torr). Thus, the impurity in air that isoriginally inside the tube 1 influencing efficiency of removing vinylmonomers from a gas stream is avoided. Besides, an aerating gas releasedfrom the aerating gas source is selected from a group consisting ofnitrogen, oxygen, helium, carbon dioxide, ozone and mixtures thereof,wherein nitrogen is preferred in this embodiment.

After step “S1” is aeration of the tube 1 designated as step “S2”, whichis exposing the photoactive-inorganic medium 121 to the aerating gas. Indetail, the controlling valve 112 mounted to the port 111 linked to theaerating gas source is opened to allow entry of nitrogen gas into thetube 1, so that water vapor in the tube 1 is further removed to reducemoisture of the photoactive-inorganic medium 121. In addition, the flowrate of the aerating gas ranges from 1 mL/min to 1500 mL/min, preferablyfrom 10 mL/min to 20 mL/min, and aeration time ranges from 1 to 36000mins, preferably from 10 to 20 mins.

Still referring to FIGS. 1 through 3, following the step “S2” is step“S3” of irradiated activation of the photoactive-inorganic medium 121,in which the photoactive-inorganic medium 121 is irradiated by the lightemitting unit 3, so as to be activated. In detail, the light emittingunit 3 is switched on to activate the photoactive-inorganic medium 121after the aerating gas is stopped from being into the tube 1. Thefollowing equation (1) shows an activation reaction of thephotoactive-inorganic medium 121 (Nano-TiO₂). Moreover, thephotoactive-inorganic medium 121 is irradiated for 1 minute to 86400minutes and preferably from 0.1 to 5 hours.

Nano-TiO₂+hυ→Nano-TiO₂*  (1)

Finally, a polymerization process designated as step “S4” is proceeded,in which a gas stream including vinyl monomers contacts with theactivated photoactive-inorganic medium 121, so that vinyl monomers inthe gas stream can join together on the surfaces of the particles of thephotoactive-inorganic medium 121 to form polymeric nano-composites.Specifically, while the gas stream including vinyl monomers flows intothe second section 142 through the first section 11, vinyl monomers inthe gas stream are initiated by the activated photoactive-inorganicmedium 121 to polymerize on surfaces of the particles of thephotoactive-inorganic medium 121, as the following equation (2) shown.Hence, the photoactive-inorganic medium 121 and the polymers thereonjointly form polymeric nano-composites. By the method of the presentinvention, vinyl monomers in the gas stream can be recovered and reusedin the form of the polymeric nano-composites.

R₁R₂C═CR₃R₄+Nano-TiO₂*→Nano-TiO₂—(R₁R₂C═CR₃R₄)_(n)  (2)

Furthermore, the gas stream including vinyl monomers contacts with thephotoactive-inorganic medium 121 for a period of time ranging from 1 to1440 minutes, and preferably from 30 to 110 minutes. The step “S4” ofpolymerization process and step “S3” of irradiated activation areproceeded under the condition of being shading from light of outerspace, namely, in the shade of the shading casing 2, and the step “S4”is proceeded in the dark with switching off of the light emitting unit3. It is noted that “vinyl monomer” is the term for any organic compoundhaving a vinyl group, for example, ethylene, propylene, butadiene,styrene and stilbene. Seeing formula “1” that is the chemical structureof vinyl monomer, R, R′, R″ and R′″ are selected from H, CH₃, CH₃CH₂ orother organic substituents. Additionally, R″ may be the same as R′″, andall of R, R′, R″ and R′″ may be H at the same time.

Taking styrene for example, a gas stream with styrene is pumped into thetube 1, and then vinyl monomers in the gas stream are effectivelyremoved as shown in FIG. 4 illustrating styrene removal efficiency withtime after the gas stream's being pumped, wherein the gas stream isformed by pumping nitrogen gas into a styrene solution because theboiling point of styrene is 98° C. If the boiling point of a chemicalthat is desired to be removed from a gas stream approximates or is lowerthan room temperature, the process described above for generatinggaseous vinyl monomers is not needed.

Since it is known that polymeric nano-composites have enhancedproperties, polymeric nano-composites produced by the present inventioncan be extensively used in the field of science and technology, thematerial of vehicle crash bars for instance.

Referring to FIG. 5, molecular weights of the polymerized vinyl monomerson the polymeric nano-composites produced by the present inventionincrease with rising the temperature in the inside of the second section12. Therefore, vinyl monomers indeed can be recovered effectively toform polymeric nano-composites by the method and apparatus for removingvinyl monomers from a gas stream of the present invention.

FIG. 6 shows an apparatus for removing vinyl monomer from a gas streamof a second embodiment according to the preferred teachings of thepresent invention. In the preferred form shown, the apparatus includes atube 4 having a first section 41, a second section 42 and a thirdsection 43, a shading casing 5 and two light emitting units 6. The firstsection 41 has a plurality of connecting ports 411 and a plurality offirst controlling valve 412 mounted to the connecting ports 411. Thereis a photoactive-inorganic medium 421 in the form of particles insidethe second section 12. The third section 43 has an outlet 431 at one endthereof and a second controlling valve 432 is mounted close to theoutlet 131. The shading casing 5 has two through holes 51 at twoopposite ends thereof, an assembling hole 52 formed in a radial wallthereof, and a reflecting face 53. The major difference between thefirst embodiment and the second embodiment is shown as the following.There is further a lid 54 covering the assembling hole 52, with one sideof the lid 54 pivotably coupling to the shading casing 5 close to theassembling hole 52. The light emitting units 6 are disposed inside theshading casing 5 through the assembling hole 52, with the light emittingunits 6 being at two opposite sides of the second section 42. By thisarrangement, the photoactive-inorganic medium 421 inside the secondsection 42 can be irradiated evenly by the light emitting units 6 toassure and accelerate activation of the photoactive-inorganic medium421.

As has been discussed above, the second section 12 or 42 is encased inthe shading casing 2 or 5 to prevent light of outer space, such thatinfluence of the light of outer space on the photoactive-inorganicmedium 121 or 421 is avoided. Furthermore, the photoactive-inorganicmedium 121 or 421 activated by the light emitting units 3 or 6 can makevinyl monomers in the gas stream to polymerize and attach to thesurfaces of the photoactive-inorganic medium 121, so as to continuouslyremove and recover vinyl monomers in the gas stream. Consequently,recovery of a usable portion of waste is allowed, and the used andsaturated photoactive-inorganic medium 121 or 421 can be utilized aspolymeric nano-composites in the future instead of being regenerated orthrown away which implies extra costs and makes the usable portion ofthe waste to become useless.

Thus since the invention disclosed herein may be embodied in otherspecific forms without departing from the spirit or generalcharacteristics thereof, some of which forms have been indicated, theembodiments described herein are to be considered in all respectsillustrative and not restrictive. The scope of the invention is to beindicated by the appended claims, rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are intended to be embraced therein.

1. An apparatus for removing vinyl monomers from a gas streamcomprising: a tube including a first section having a connecting portwith an opening, a second section, and a third section having an outlet,with the three sections sequentially linking together, with the secondsection connecting between the first section and the third section, andwith a photoactive-inorganic medium being arranged inside the secondsection; a shading casing surrounding and sealing the second section,with an inner surface of the shading casing defining a reflecting face;and a light emitting unit being mounted to the shading casing toirradiate and activate the photoactive-inorganic medium in the secondsection.
 2. The apparatus for removing vinyl monomers from a gas streamas defined in claim 1, wherein the shading casing has an assembling holeformed in a wall thereof, and the light emitting unit is coupled to theassembling hole and seals the assembling hole.
 3. The apparatus forremoving vinyl monomers from a gas stream as defined in claim 1, whereinthe shading casing has an assembling hole formed in a wall thereof, witha lid covering the assembling hole.
 4. The apparatus for removing vinylmonomers from a gas stream as defined in claim 3, wherein the lightemitting unit is arranged inside the shading casing.
 5. The apparatusfor removing vinyl monomers from a gas stream as defined in claim 3further includes a light emitting unit, with the two light emittingunits being arranged inside the shading casing and at two opposite sidesof the second section.
 6. The apparatus for removing vinyl monomers froma gas stream as defined in claim 1, wherein the shading casing furtherhas two through holes, with the tube partially received in the shadingcasing through the through holes.
 7. The apparatus for removing vinylmonomers from a gas stream as defined in claim 1, wherein the reflectingface is white.
 8. The apparatus for removing vinyl monomers from a gasstream as defined in claim 1, wherein the inner surface of the shadingcasing is daubed with white paint or attached with white cloth or paperto form the reflecting face.
 9. The apparatus for removing vinylmonomers from a gas stream as defined in claim 1, wherein the lightemitting unit is able to emit UV or visible light.
 10. A method forremoving vinyl monomers from a gas stream comprising the steps of:irradiating a photoactive-inorganic medium by a light emitting unit toactivate the photoactive-inorganic medium; and pumping a gas streamincluding vinyl monomers to contact with the activatedphotoactive-inorganic medium to make the vinyl monomers in the gasstream to polymerize on the photoactive-inorganic medium to jointly forma polymeric nano-composite.
 11. The method for removing vinyl monomersfrom a gas stream as defined in claim 10, wherein thephotoactive-inorganic medium is irradiated merely by light from thelight emitting unit, and the gas stream including vinyl monomerscontacts with the activated photoactive-inorganic medium in the dark.12. The method for removing vinyl monomers from a gas stream as definedin claim 10, wherein a step of aerating the photoactive-inorganic mediumby an aerating gas is added before irradiating the photoactive-inorganicmedium for reducing moisture of the photoactive-inorganic medium. 13.The method for removing vinyl monomers from a gas stream as defined inclaim 12, wherein a step of heating the photoactive-inorganic medium inlow pressure lower than 1 atm is added before aerating thephotoactive-inorganic medium.
 14. The method for removing vinyl monomersfrom a gas stream as defined in claim 10, wherein vinyl monomer isselected from ethylene, propylene, butadiene, styrene or stilbene. 15.The method for removing vinyl monomers from a gas stream as defined inclaim 10, wherein vinyl monomer has a chemical structure as thefollowing, with R, R′, R″ and R′″ being selected from H, CH₃ or CH₃CH₂.


16. The method for removing vinyl monomers from a gas stream as definedin claim 10, wherein the light emitting unit is able to emit UV light orvisible light.
 17. The method for removing vinyl monomers from a gasstream as defined in claim 10, wherein the photoactive-inorganic mediumis irradiated for 1 minute to 86400 minutes.
 18. The method for removingvinyl monomers from a gas stream as defined in claim 10, wherein the gasstream including vinyl monomers contacts with the photoactive-inorganicmedium for a period of time ranging from 1 minutes to 1440 minutes. 19.The method for removing vinyl monomers from a gas stream as defined inclaim 12, wherein the aerating gas is selected from a group consistingof nitrogen, oxygen, helium, carbon dioxide, ozone and mixtures thereof.20. The method for removing vinyl monomers from a gas stream as definedin claim 12, wherein the photoactive-inorganic medium is aerated by theaerating gas for a aeration time ranging from 1 minute to 36000 minutes.